This invention is directed to the conveying of small particles from one location to another and in particular to a conveyor which uses electric fields to provide the translation motion to the charged particles.
The conveying of small particles is an important industrial operation which is generally accomplished by a moving belt, a screw or other mechanical devices. In the process the fine particles enter between the various mechanical parts and depending on their abrasiveness the life of the mechanical conveyor is either limited or the conveyor itself requires substantial maintenance.
In addition to mechanical conveyors there are electromagnetic conveyors which accomplish the translational motion of the material by means of a special vibration. Such feeders have stationary electrical coils for energizing the vibration. The limitations of this type of feeder are in their large mass which is needed for the vibration by means of magnetic fields.
Finally a short electrostatic conveyor has been developed by Senichi Musada and has been described in U.S. Pat. No. 3,778,678 which issued on Dec. 11, 1973, and in U.S. Pat. No. 3,872,361 which issued on Mar. 18, 1976. This conveyor consists of a tubular duct of insulating material having elongated electrodes curved concentrically about the duct as axially spaced rings or interwound spirals. The electrodes are connected with the terminals of an alternating current source to produce a wave-like electric field within the duct by which the particles are repelled from the inner duct surface and repulsively propelled in one lengthwise direction along the duct. In this system centrifugal forces are used to hold the charged particles in suspension while the electric field reversals cause the rotation which lead to unidirectional movement.